MART Vol. II MO/MP - NESA - Civil Air Patrol

Figure 7-4Figure 7-5Upon hearing the null, the observer should quickly look at the headingindicator. If the search aircraft is a low-wing aircraft, like the Cherokee, look forthe number adjacent to the imaginary aircraft's low wing, as shown in Figure 7-4.If the search plane is a high-wing, like the Cessna 172, look for the numberadjacent to the imaginary plane's high wing, as shown in Figure 7-5. Thatnumber is the magnetic bearing from the search aircraft’s present position to theELT transmitter.Regardless of the method used to determine the ELT magnetic bearing, thenext step is to convert that magnetic bearing to a true bearing by adding orsubtracting the published magnetic variation for that area. Then draw a line onyour chart from the search aircraft's known position in the direction of thecalculated true bearing. You now have one null vector, or line of position, to theELT. The ELT is somewhere along that line, but it isn’t possible to tell exactlywhere. To narrow the focus, simply repeat the process starting from anotherknown position over a different geographical point. Don’t pick your nextgeographical point near to or along the initial null vector. The accuracy of thistechnique improves if you select geographic points well away from each other. If125